Heat Transfer and Friction Characteristics of Perforated Fin with a Longitudinal Slot under Forced Convection

Extended surfaces are used in a variety of heat transfer applications owing to their ability in reducing the convection resistance by exposing a large surface area to the surrounding fluid. Surface modification in the form of perforations is a passive method of increasing the heat transfer rates with the additional benefit of weight reduction. This work deals with numerical investigation of heat transfer and friction from a perforated fin (with and without slot) subjected to forced convection. The perforated fin with slot has been found to have a maximum enhancement in heat transfer with the simultaneous increase in frictional losses versus that of a solid fin. Further, the perforated fin without slot has been able to transfer heat at a relatively higher rate with a considerable reduction in energy loss due to friction in comparison to a solid fin.     

Assessment of the validity of maturity metrics for predicting the volatile composition of Concord grape juice

Total soluble solids (TSS) are typically used as the sole metric for maturity of Concord grapes. However, the reliability of TSS in predicting the aroma composition of finished juice for grapes sourced from multiple sites has not been investigated. This study sought to determine the validity of TSS in predicting the aroma composition of the juice while also investigating other potentially useful indicators, including pH, titratable acidity (TA), and TSS:TA ratio. Grapes were harvested from 9 sites in the Lake Erie Concord Grape Belt and stratified from north to south and east to west. The key aroma compounds methyl anthranilate ("grapey") and trans-2-hexenal ("herbaceous") were quantified along with several other odorants. It was observed that while TSS was a robust predictor of monomeric anthocyanin content across sites, it was a poor predictor of aroma compounds in the finished juice. Conversely, pH, TA, and TSS:TA ratio were all significantly correlated with methyl anthranilate and trans-2-hexenal concentrations (P < 0.05) in samples equal to or exceeding 15 Brix, the industry minimum for grape maturity. These results indicate that parameters related to acidity are better predictors of aroma composition than TSS, which may aid in efforts to minimize herbaceous off-aromas and optimize the aroma composition of the finished juice.     

Effect of organoclay on the gas barrier properties of natural rubber nanocomposites

Natural rubber nanocomposites have been prepared with organically modified montmorillonite clay. The nanocomposites have been characterized by X‐ray diffractometry and transmission electron microscopy. The gas‐barrier properties of the nanocomposites have been studied for three different gases viz., oxygen, nitrogen, and CO₂ gases. The natural rubber–organoclay composites exhibit outstanding gas‐barrier properties compared to the neat rubber. Various models have been applied to predict the decrease in permeability in nanocomposites. All other models except Bharadwaj model give low values of calculated aspect ratio. Dynamic mechanical analysis has been carried out to investigate the role of the constrained region on the permeability of the nanocomposites. The permeability decrease of the organoclay nanocomposites is found to have good qualitative correlation with the volume of the constrained region. POLYM. COMPOS.,, 2012. © 2012 Society of Plastics Engineers     

Traffic grooming in WDM optical network with grooming resources at Max Connectivity nodes

In this paper, we propose Max Connectivity grooming in WDM mesh networks under static lightpath connection requests. The grooming and wavelength conversion resources are placed at the nodes having maximum connections. We propose a heuristic genetic algorithm (GA) model to solve grooming, routing and wavelength assignment. The GA algorithm has been used to optimize the cost of grooming and wavelength conversion resources. The blocking probability has been investigated under different lightpath connections. The performance of Max Connectivity grooming has been compared with other grooming policies. Our results indicate the improvement of resource utilization with minimum blocking probability.     

Effect of surfactant and heat treatment on morphology,surface area and crystallinity in hydroxyapatite nanocrystals

Hydroxyapatite (HA) powders were synthesized by the wet precipitation method, with and without surfactant, under identical processing parameters. These powders were then heat treated at 900 °C for 3 h in air. The detailed characterization of the powders was done by using SEM, dynamic light scattering, nitrogen adsorption, XRD, Raman spectroscopy, and FTIR techniques. The HA phase, identified by well defined PO₄^3? and OH^? ion peaks in Raman and FTIR spectra, was observed in all the powder samples. The addition of surfactant changed the morphology of the particles from spherical to needle/rod-like structure and increased the surface area up to three times (from 33 to 96 m²/g). Also, suppression in the evolution of β-TCP phase was observed along with decrease in the crystal size and crystallinity of the powder due to the addition of surfactant. Synthesized nano-HA crystals were found to have diameters and lengths in the range 10–25 nm and 75–150 nm, respectively. The heat treatment changed the architecture of the particles, increased the crystallinity and reduced the surface area to ≈7 m²/g. However, the relative increase in crystallinity was much higher for the powder synthesized with surfactant. The ratio of the average crystallite size to the crystallinity degree was about 0.53±0.07 for all the powders. The particle size distribution was bimodal and coarser for the powder synthesized without surfactant. The pore size analysis showed transformation of a predominantly mesoporous structure into a meso- plus macroporous one on heat treatment. The intensity of OH^? group peak in Raman spectra was found to be highly sensitive to the crystalline state of the HA powder and may be used to assess crystallinity.     

Preparation and characterisation of Tl2Pu(MoO4)3 and Tl4Pu(MoO4)4 in Tl-Pu-Mo-O system by X-ray and thermal methods

The quaternary Tl-Pu-Mo-O system was investigated for the first time and two new quaternary compounds Tl₂Pu(MoO₄)₃ and Tl₄Pu(MoO₄)₄ were synthesized by solid state reactions of Tl₂MoO₄ with Pu(MoO₄)₂ in 1:1 and 2:1 molar proportions at 773 K and 823 K, respectively. X-ray powder diffraction data of these compounds were indexed on orthorhombic system. Thermogravimetric (TG) curves of Tl₂Pu(MoO₄)₃ and Tl₄Pu(MoO₄)₄ were recorded in air and no significant weight changes were observed up to 973 K and 1033 K, respectively. Differential thermal analysis (DTA) curves of Tl₂Pu(MoO₄)₃ and Tl₄Pu(MoO₄)₄ showed endothermic peaks due to the melting of the compounds at 838 K and 1013 K, respectively. Non-isothermal kinetics of decomposition of Tl₂Pu(MoO₄)₃ and Tl₄Pu(MoO₄)₄ in air was studied using thermogravimetric technique. Tl₂Pu(MoO₄)₃ and Tl₄Pu(MoO₄)₄ when heated up to 1673 K decomposed to Tl₂O and MoO₃ in the gaseous form, giving solid PuO₂ as an end product. The reactions followed unimolecular nucleation and growth mechanism with activation energies of 106 kJ/mol and 157 kJ/mol, respectively.     

Characterization of the dry high speed drilling process of woven composites using Machinability Maps approach

Damage to woven carbon fiber composites and high tool wear are the main challenges in drilling processes. The effect of speeds and feed rates on the damage mechanisms, namely, delamination, surface roughness, fiber pullout, thermal damage, hole circularity and hole diameter error were established using a newly introduced concept of Machinability Maps. Using an instrumented tool, the cutting temperature was measured. The results showed that the effect of tool wear on the quality maps can be established through the changes in the thrust and cutting forces.     

Thermal expansion studies on Th(MoO4)2, Na2Th(MoO4)3 and Na4Th(MoO4)4

Thermal expansion behavior of Th(MoO₄)₂, Na₂Th(MoO₄)₃ and Na₄Th(MoO₄)₄ was studied under vacuum in the temperature range of 298–1123 K by high temperature X-ray diffractometer. Th(MoO₄)₂ was synthesized by reacting ThO₂ with 2 mol of MoO₃, at 1073 K in air and Na₂Th(MoO₄)₃ and Na₄Th(MoO₄)₄ were prepared by reacting Th(MoO₄)₂ with 1 and 2 mol of Na₂MoO₄, respectively at 873 K in air. The XRD data of Th(MoO₄)₂ was indexed on orthorhombic system where as XRD data of Na₂Th(MoO₄)₃ and Na₄Th(MoO₄)₄ were indexed on tetragonal system. The lattice parameters and cell volume of all the three compounds, fit into polynomial expression with respect to temperature, showed positive thermal expansion (PTE) up to 1123 K. The average value of thermal expansion coefficients for Th(MoO₄)₂, Na₂Th(MoO₄)₃ and Na₄Th(MoO₄)₄ were determined from the high temperature data.     

Fuel wood consumption pattern of tribal communities in cold desert of the Lahaul valley, North-Western Himalaya, India

Fuel wood is the primary source of energy in rural areas of the Himalaya. Lack of resources, extremely low temperature and xeric climatic conditions of the study region (Khoksar – 3200 m, Jahlma – 3000 m, Hinsa – 2700 m and Kuthar – 2600 m) of cold desert of the Lahaul valley has led to serious deforestation due to excessive use of fuel wood in the past. On the basis of family sizes, fuel wood consumption was recorded less in large family as compared to small family. The fuel wood is used for various activities such as cooking, water heating, room heating, lighting and livestock rearing, etc. Fuel wood consumption was highest in high altitude villages as compared to low altitude villages irrespective of family size. Fuel wood consumption of 4.32 ± 0.99 kg/capita/day was highest at Khoksar for small family during winter season followed by the autumn (2.25 ± 0.15 kg/capita/day) and summer (1.38 ± 0.13 kg/capita/day). The labour energy expenditure for fuel wood collection was also highest for Khoksar (91.91 MJ/capita/year), followed by Hinsa (61.29 MJ/capita/year), Kuthar (52.01 MJ/capita/year) and Jahlma (51.89 MJ/capita/year), respectively. It was found that fuel wood consumption in the study region was influenced by the local cold climate and season of the year. The present information on fuel wood consumption pattern at different altitudes would be helpful in designing appropriate technologies to develop energy plantations in the region.     

Cattaneo–Christov double-diffusion model with Stefan blowing effect on copper–water nanofluid flow over a stretching surface

We often encounter many processes where the cooling rate is a key factor in deciding the features of a desired product. Due to increasing demands of controlled cooling systems, an effort is made to theoretically study the effect of volume fraction on mixed convective Cu–water nanofluid flow over a stretching surface with activation energy and thermal radiation. The nonlinear dynamical system is simplified using apt similarity variables and the obtained ordinary differential equations are dealt numerically using Runge–Kutta–Fehlberg method and shooting scheme. The thermal and solutal equations are modeled considering Cattaneo–Christov double-diffusion model. The flow problem is studied considering velocity slip and zero mass flux state at the surface. As a novelty, the present case considers the blowing effect at the surface to study massive species transport during nanofluid flow with Cattaneo–Christov double-diffusion model. The results show that an increase in strength of thermal radiation increases temperature and buoyancy ratio parameter, thereby escalating the skin friction coefficient. When thermal relaxation parameter changes from 0.001 to 0.005, heat transfer coefficient improves by 24.36%. Furthermore, with the change in value of the blowing parameter from 0.1 to 0.1015, the maximum value concentration of nanoparticles that is attained during the flow is increased by 7.15%.